1. Field of the Invention
This invention relates to a riser sleeve structured so that when used in casting, the riser is cast integrally with a projecting portion for receiving one wedge blade of a riser breaker of the type that breaks a riser off of a main casting at a neck portion of the riser by an opening force applied between a pair of opposing wedge blades (this type of breaker being hereinafter called an xe2x80x9copenable wedge blade type riser breakerxe2x80x9d).
2. Description of the Prior Art
In the production of castings, the openable wedge blade type riser breaker (taught by, for example, Japanese Utility Model Publication No. Hei 2-31250 and Japanese National-Publication No. 56-500247) is widely used for breaking the riser (and/or runner) off of the main casting. This breaker has been extensively adopted owing to its ability to upgrade casting efficiency and markedly improve the working environment.
Up to now, however, this type of breaker has been limited in application. In use, its pair of opposing wedge blades are inserted between the main casting and a side surface of the riser and force is applied to the wedge blades to separate them and break off the riser. The breaker is therefore suitable for use with a side riser, which the wedge blades can secure a hold on, but cannot be used with a top riser (a riser formed on top of the main casting) because, even if one of the wedge blades can be seated on top of the main casting, no appropriate projection is present to offer a hold for the other of the paired wedge blades.
It has been proposed to overcome this problem occurring in the case of the top riser by using a jig that serves as a projection providing a wedge blade seat. This would be extremely uneconomical, however, in view of the need to stock countless jigs corresponding to castings of many and varied shapes. Moreover, since a jig would have to be installed on each casting, a complex and time-consuming jig installation step, highly inappropriate for industrial production, would be necessary.
Cleaving of the top riser at a reduced-diameter neck portion is commonly facilitated by giving the riser sleeve a vertical sectional configuration narrowing toward the bottom in a V- or U-like shape or by installing a neck-down core at the bottom of the riser sleeve. In the case of ordinary cast iron, these techniques enable the riser to be detached easily with a hammer or the like, but in the case of cast steel, which, unlike ordinary cast iron, has high-strength material properties, the practice has been to remove the riser by flame cutting with a gas torch or by striking it with a large hammer. For similar reasons, a large hammer is also used for riser removal in the case of cast ductile steel. The work of knocking a riser off manually with a large hammer is not only extremely dangerous for the worker concerned, but it further produces undesirable working conditions for many other workers in the vicinity. It also degrades the general working environment.
These circumstances have made it difficult to enjoy the considerable improvement in casting yield offered by the top riser casting method and forced adoption of the side riser method instead.
An object of the invention is therefore to provide a riser sleeve capable of imparting a top riser with a shape enabling use of an openable wedge blade type riser breaker for detachment of the top riser directly, without use of a special jig.
To achieve this object, the invention provides a riser sleeve comprising a sleeve body and an evaporative pattern fit into the sleeve body to pass through a side wall thereof, the evaporative pattern being shaped to enable casting, integrally with a riser cast by the sleeve body, of a projecting portion capable of receiving a wedge blade of an openable wedge blade type riser breaker for breaking a riser off a main casting at a neck portion by an opening force applied to a pair of wedge blades.
The riser sleeve can be a blind riser sleeve or an open riser sleeve.
The blind or open riser sleeve can be configured to have a cross-section taken along its vertical axis that narrows toward the bottom in a V- or U-like shape.
The riser sleeve of any of the foregoing configurations can be provided at its bottom with a neck-down core.